Fluoride release and shear bond strengths of three light-cured glass ionomer cements

Little is known about the release of fluoride from light-cured glass ionomer cements when used as orthodontic bonding agents. Fluoride release from three "hybrid" light-cured glass ionomer cements was measured during a 42-day period after initial curing in an in vitro test that simulated their use as orthodontic bonding agents. On day 48, the bonded teeth were exposed for 30 seconds to a stannous fluoride gel and checked for fluoride release during the following week. One cement (BL) released the most fluoride after initial cure and after an exposure to a stannous fluoride gel on day 48. The other two hybrid cements exhibited both significantly less fluoride release than material (BL) and resembled for most of the 55-day duration the composite resin control. After the 55-day duration, shear bond strengths of the composite resin control were significantly higher than the three light-cured glass ionomer cements. The light-cured glass ionomer cements in this study released fluoride after initial curing and after exposure to a topical fluoride gel. This property may help reduce or possibly even prevent enamel decalcifications seen around bracket bases. At present, the shear bond strengths of the light-cured glass ionomer cements tested appear to be too low for routine orthodontic bonding agents.